It has previously been shown that some human tumor cells contain oncogenes derived from activated protooncogenes which are believed to play an important role in the origin, progression or maintainence of these tumors. Identification of these oncogenes in a physiological system would be a useful diagnostic tool in the identification or detection of their respective tumor systems.
The oncogenes activated in certain human tumors whose DNA is able to morphologically transform the mouse NIH/3T3 fibroblasts have been found to represent members of the ras gene family. The ras genes are eukaryotic genes encoding for immunologically related proteins of 21.000 MW (p21) which were initially found in the genome of certain animal RNA tumor viruses, in particular, the viruses of Harvey and Kirsten. The human gene homologue to the oncogene of the Harvey virus (c-H-ras) has been found activated in some tumor cell lines derived from bladder carcinomas and lung carcinomas. The oncogene of other tumor cell lines derived from neuroblastomas (the SK-NS-H cell line), leukemia and other types of cancer, has been identified as another member of the ras family and has been named N-ras.
The oncogene originally found in certain colon (the SW480 and SK-CO-1 cell lines) and in certain lung (the Calu-1 and SK-LU-1 cell lines) carcinomas, which has been posteriorly found in a broad range of human tumors is the human homologue of the Kirsten virus oncogene (c-K-ras).
The mechanisms by which these oncogenes have been activated from their corresponding protooncogenes in these human tumors has been established as point mutations in their protein coding regions (exons). Thus, the c-H-ras oncogene present in the T24 bladder carcinoma cell line has been activated by a single base substitution at position 12 of the first coding exon (Capon, et al., (a) Nature, 302, 33 (1983); Tabin, et al., Nature, 300, 143 (1982); Reddy, et al., Nature, 149 (1982); Taparowsky, et al., Nature, 300, 762, (1982) which results in the substitution of glycine by valine in this position of the P21 protein. The oncogene of the Hs242 lung carcinoma cell line has been activated by a mutation in the second coding exon, at position 61, which results in the substitution of glutamine by leucine (Yuasa, et al., Nature, 303, 775 (1983).
The N-ras oncogene present in the SK-NS-H neuroblastoma cell line has been activated by a base substitution at position 61 of the second exon which results in the substitution of glutamine by lysine (Taparowsky, et al., Cell, 34, 581-86 (1983).
The c-K-ras oncogene present in the Calu-1 cell line has been activated by a point mutation at position 12 of the first exon which results in the substitution of glycine by cysteine (Shimizu, et al., Nature, 304 497 (1983), Capon, et al.(b), Nature, 304, 507, 1983b)). The c-K-ras oncogene present in the SW480 colon carcinoma cell line contains a mutation at the same position 12 which results in the substitution of glycine by valine (Capon, et al. (b), supra (1983).
Prior to the work leading to the present invention, no mutations have been found or identified in c-K-ras oncogenes other than codon 12 of the first exon.